In a WDM (Wavelength Division Multiplexing) system, light of different wavelengths is transmitted in a link. Because of SRS (Stimulated Raman Scattering), optical power of a short wavelength transfers to optical power of a long wavelength. In addition, a gain spectrum and noise figure spectrum of an OA (Optical Amplifier) in the link are not flat for all wavelengths, and loss of different wavelengths caused by the link is not consistent. Therefore, for signals of different wavelengths, though with the same power and OSNR (Optical Signal to Noise Ratio) at a transmitter end, the power and OSNR may be substantially different after long-distance transmission, resulting in substantially different service performance of different wavelengths received at a receiver end. In the WDM system, the performance of a link is constrained by a wavelength with the worst transmission performance carried by the link. Therefore it is crucial to equalize transmission performance of wavelengths in a link through adjusting optical power of the wavelengths.
In practice, to enable different wavelengths in a same optical fiber to have the same or similar transmission performance, an equalization operation needs to be performed only on optical power and optical signal to noise ratios of the different wavelengths to ensure that the wavelengths have the same or similar transmission performance. Currently, an OSNR equalization subsystem and optical power equalization subsystem are arranged at each adjusting point in an optical link. The OSNR equalization subsystem detects OSNR differences between wavelengths, compares OSNRs of the wavelengths with a stored OSNR reference value, and increases or attenuates the OSNRs of the wavelengths to the OSNR reference value according to a comparison result. After the OSNRs of the wavelengths are equalized, the optical power equalization subsystem detects optical power of all wavelengths, compares the optical power of the wavelengths with a stored optical power reference value, and increases or attenuates the optical power of the wavelengths to the optical power reference value.
In a practical application, the prior art has a problem because, as adjustment at a previous adjusting point affects an optical power change at a next adjusting point, only serial adjustment can be performed on each adjusting point, and for a complex ring network, an adjustment process is an iteration process, and is rather time-consuming. In addition, as each adjusting point makes adjustment while performing detection, the adjustment may only be carried out after an optical path is connected.